Collision theory and activation energy

• Collision theory explains how various factors affect rates of reactions.
• Collision theory is when chemical reactions can occur only when reacting particles collide with each other and with sufficient energy
• The minimum amount of energy that particles must have to react is called what ?

  Activation energy
• Increasing the concentration of reactants in solution, the pressure of reacting gases, and the surface area of solid reactants increases the frequency of collisions and so increases the rate of reaction.
• Increasing the temperature increases the frequency of collisions and makes the collisions more energetic, and so increases the rate of reaction.
• • Prediction: Increasing the concentration of reactants will result in a higher reaction rate.
  • Explanation: According to collision theory, the rate of reaction is directly proportional to the number of effective collisions between reactant particles. Higher concentration means a greater number of particles per unit volume, leading to more frequent collisions and an increased likelihood of successful collisions.
• Changing Pressure (for Gases):

  • Prediction: Increasing the pressure of reacting gases will result in a higher reaction rate.
  • Explanation: In gases, increasing pressure reduces volume, effectively increasing the concentration of gas particles. According to collision theory, this increase in concentration leads to more frequent collisions, promoting a higher reaction rate.
• Changing Temperature:

  • Prediction: Increasing the temperature will result in a higher reaction rate.
  • Explanation: Higher temperatures provide particles with more kinetic energy, increasing the frequency and energy of collisions. According to collision theory, a higher proportion of collisions will have energy exceeding the activation energy, leading to more effective collisions and an increased reaction rate.
• reducing the size of pieces of a reacting solid enhances the surface area-to-volume ratio, facilitating more frequent and effective collisions between reactant particles and, consequently, increasing the overall reaction rate.
• Proportionality when using collision theory:

  In simpler terms, it's like having more players in a game – the more reactant molecules (players), the more collisions, and the faster the reaction proceeds. This simple idea illustrates the proportional relationship between concentration and reaction rate according to collision theory.